Photoelectric checking circuits



May 4, 1954 J. A. BRUSTMAN 2,677,815 PHOTOELECTRIC CHECKING CIRCUITSFiled Dec. 4, 1951 5 SheetsSheet l by N JOSEPH A. BRUSTMAN BY ATTORNEY My 4, 1954 J. A. BRUSTMAN 2,677,815

PHOTOELECTRIC CHECKING CIRCUITS Filed Dec. 4, 1951 r 5 Sheets-Sheet 2PHOTOELECTRIC CELLS (UPPER) PHOTOELECTRIC CELLS (LowER) INVENTOR. JOSEPHA. BRUSTMAN J TI II MW.

ATTORNEY May 4, 1954 J. A. BRUSTMAN PHOTOELECTRIC CHECKING CIRCUITSFiled Dec. 4, 1951 5 Sheets-Sheet 3 FIG. 4

DRUM ROTATION.

FIG.5

+|Oov TO DECODER INVENTOR. JOSEPH A. BRUSTMAN AT TOR NEY May 4, 1954 J.A. BRUSTMAN 2,677,815

PHOTOELECTRIC CHECKING CIRCUITS Filed Dec. 4, 1951 5 Sheets-Sheet 4 III![III 9| SEGMENT INVENTOR.

74 JOSEPH A. BRUSTMAN ATTORNEY NO HOLE 7* May 4, 1954 Filed Dec. 4, 1951J. A. BRUSTMAN PHOTOELECTRIC CHECKING CIRCUITS Sheets-Sheet 5 FIGS S NING S1 52 T1 T2 T3 G A T COLUMN L R R R R L R I I CLOSED COND. 9|(sPAqE) OPEN NON-C. 92 (6 HID LES) II II 93 (SPACE) II II 94(6 HOLES)CLOSED COND. 95 (SPACE) II II J FIGQ I 51 I I l I I I I I I I l I I I IT 82 I I I I I I I I T102) I I\ I k I I I 'I I T1 L) I\ I I k I I I I II I T T2 I I I\ I I l I I .I I T3(R) II I I\ I I l l I UL) k I I I -I Io t2 t3 t4 t5 INVENTOR.

JOSEPH A. BRUSTMAN Jim ATTORNEY Patented May 4, 1954 2,677,815PHOTOELECTRIC CHECKING CIRCUITS Joseph A. Brustman, Fairfield, Conn.,assignor to Remington Rand Inc., New York, N. Y., a corporation ofDelaware Application December 4, 1951, Serial No. 259,865

12 Claims.

This invention relates to photoelectric checking systems and hasparticular reference to the checking and testin of photoelectric cellswhich are employed in data card sensing. While the invention is subjectto a wide range of applications, it is especially suited for use in datacard machines where information is obtained from the perforations cut indata cards and used for calculating systems and tabulator work. As usedthroughout the specification and claims, the term photoelectric cellrefers not only to the usual type of vacuum tube cell but also to anyrelated transducer which is sensitive to light and produces electricalvariations in response to light variations.

Photoelectric cells have been used for sensing data cards and also forsensing the presence of light-masking material in many industrialapplications. However, they have a definite useful life and when they gobad, there is no visual indication of the transition. The photoelectricmaterial on the cathode may be damaged or the tube may lose its vacuum.In either case, only an electrical test will indicate the lack ofsensitivity. The present invention contemplates testing eachphotoelectric cell for its response to light and also for its lack ofresponse when dark. These two tests are made after each data card hasbeen sensed. In the case of a failure, a mechanical clutch may bedisengaged to stop the sensing operation or some other form of indicatormay be operated to show the operator of the machine that something iswrong.

One of the objects of this invention is to provide an improvedphotoelectric checking system operating intermediate sensing of eachdata card, thereby providing instant check on the photoelectric system.

Another object of the invention is to provide a checking system whichtests the photoelectric amplifying system and the decoding systemsemployed in conjunction with the sensing of the data cards.

Another object of the invention is to provide a checking system whichoccupies little space and consumes a very short time for its operation.

Another object of the invention is to provide a photoelectric checkingsystem which requires few extra tubes and circuits for its operation.

The invention comprises a series of slots and masks on a sensing drumwhich applies one or more cycle of luminous energy to all the sensingcells. Each of these cycles includes a period of light and a period ofdarkness. The system also includes the usual photoelectric amplifiersand decoding system used in the sensing operation. The decoding systemis employed to produce a first electric signal when all of the cells areconducting and for producing a second electric signal when all of thecells are non-conducting. These two signals are applied to a countingcircuit comprisin a plurality of trigger circuits which are actuated bythe two signals and caused to transfer their conductance from one set ofelectrodes to another. If a complete set of counts is received, thesensing mechanism continues to operate but if an incomplete set ofcounts is received, a signal is produced indicating that all the cellsare not working properly and the machine should be stopped.

The invention also contemplates the use of an automatic clutch whichdisconnects the sensing mechanism from a driving motor whenever a fullcount is received.

For a better understanding of the present invention together with otherand further objects panying drawings:

Fig. 1 is a side view, partly in section, of the sensing mechanism andincludes a sensin drum and a card feeding mechanism.

Fig. 2 is an isometric view, greatly simplified, indicating the path ofthe data card around the sensing drum and showing one of cells in onegroup.

Fig. 3 is a block diagram of the entire circuit showing thephotoelectric cells, the decoder and the counting circuit.

Fig. 4 is a plan view showing a section of the sensin drum indevelopment.

Fig. 5 is a detailed diagram of connections of a control system which isemployed to energize the decoding system each time a column is sensed inthe data card.

Fig. 6 is a schematic diagram of connections of the photoelectric cellamplifier.

Fig. '7 is a schematic diagram of connections of the counting circuitwhich receives electric from the decoding system, counts the nd appliesthe results to a signal circuit.

Fig. 8 is a chart which indicates the conductivity of the two inputtrigger circuits and the three countin trigger circuits which make upthe pulse counting circuit.

Fig. 9 is a graph showing voltage pulses as applied to the varioustrigger circuits.

Referring now to Fig. 1, the sensing mechanism includes a card chamberill where the data cards may be stacked preliminary to the sensingoperation. A picker knife l l is secured to a movable base H. which maybe moved into engagement with the lowest card in the stack by means of amechanical oscillating system. which includes a link l3, rockable leversi l and i5, and an eccentric arm it which is mounted on an eccentric hub[1. When the picker knife H is moved toward the rear of the machine, itengages the lowest card in the stack and forces it through a throat to apair of card rollers 2%. These rollers move the card into the positionshown in Fig. l where the front edge of the card 2! is' forced intoengagement with a clamp 2.2 which is spring mounted on the periphery ofa card sensing drum 23. This drum rotates continually on a shaft 24 andhas a periphery somewhat longer than the length of four cards. When thedrum 23 advances to the position just prior to that shown in Fig. l,clamp 22 is held in a disengaged position by a cam arrangement insidethe drum (not shown). As soon as the card is forced under the clamp, theclamp is rotated about a pivot 25 so that the card is firmly held by itsfront edge and thereafter, for one-half revolution of the sons-- ingdrum, is securely held by the clamp and is pressed against the peripheryof the drum by idling rollers 26 and 21.

During the passage of the card around the drum it passes through asensingposition 36. A source of light 35 is positioned under the drumsurface and light from the source is directed outwardly, shining throughholes in the card and being received by a set of photoelectric cells 32mounted outside or the drum but in close proximity to the drum surface.The cards used in this sensing system are the usual data cards punchedin the well-known Powers code and are divided into two fields or areas,an upper and a lower. The cards have 45 columns in each field and eachcolumn contains six data positions. The first sensing arrangement isused to sense the data holes in the upper field and a second sensinposition 33 is employed to sense the data holes in the lower field. Thesensing position is similar to the first position as and contains asource of light 34 and a series of photoelectric cells 35. These twosensing positions are mount-- ed 90 apart around the periphery of thesensing drum 23.

The simplified drawing 2 shows the card stack IE3 and a data card 225which has just entered the first sensing position and is under a seriesof photoelectric cells 32. Another card 2i is shown leaving the secondsensing position, having just passed under the collection ofphotoelectric cells 35. Light sources 3! and 3B are indicated in thisfigure mounted on shaft i l. The first set of photoelectric cells 32covers only the upper half of the data card and senses positions 1 to 45inclusive. The second set of photoelectric cells senses the lower halfof the data card which includes data positions 46 to 90, inclusive. Thetwo sensing positions are arranged slightly less than 90 apart aroundthe periphery of the drum and are spaced so that the second set of cellsstarts sensing column 46 in regular sequence after the first set ofcells 32 has sensed column 45. After a data card has passed the secondset of photoelectric cells 35 and before a following card has enteredthe sensing position 3d, a series of light and dark illumination periodsis applied to each group of cells in a sequence arrangement whichresults in two cycles of luminous energy.

The arrangement of slots and masks are better illustrated in Fig. 4where a development of the drum periphery is shown in greater detail. Inthis drawing a data card 38 is shown leaving the second sensing positionwhile another data card 31 is shown entering the first sensing position.The data card is arranged so that the last or ninetieth columnperforations appear in that area of the card 3%; designated by thefigure 50. Between this column and the right-hand edge of the card nodata holes are ever punched and, therefore, it always produces a periodof darkness as sensed by the photo cells. Two additional column areas 92and 93 are indicated on the drum periphery and also act as a mask.Column 94, however, comprises a cut-out portion it and when this slotpasses beneath the photoelectric cells, all six cells are illuminated. Asimilar arrangement comprising a single slot Al in the ninetysecondposition is out in the drum periphery two column spaces away from theleading edge of card 31. The first data column of card 3? is indicatedin Fig. 4 by the numeral l and between this data column and the leadingedge of the card there is a card area as which never contains any dataholes. Columns 93 and 84 represent masked column areas between the openslot ii and the leading edge of the card.

In. order to determine the sequence of pulses as delivered to theamplifying system, it must be understood that the two sensing systems soand 33 are spaced iorty five columns apart and when one set of cells isabove column 9! on card 3b, the other set of cells is above column 9!adjoining open slot M in the position of column 92. In this position(column 9 I) both sets of cells are blanked off and receive noillumination. When the drum rotates so that columns 92 are below thecell positions, then all six of the photo cells in the first positionwill receive light through slot 4| while the six cells in group 35 arein darkness. When the drum rotates to column position 93, both groups ofcells are again in darkness. Another increment of rotation to position94 permits all six cells in group 35 to receive illumination throughslot 46 while the first set of cells 32 are in darkness. Columns 95produce no illumination for either group of cells and then column 1 ofcard 3'! may or may not produce light for one or more of thephotoelectric cells in group 532, depending upon the data punched in thecard.

As indicated in Fig. 6, the two photoelectric cells for each dataposition are parallel con nected to each other. Therefore, the sequencejust outlined produces in the photoelectric cell amplifier a period ofillumination at position 92, a period of darkness at position 93, asecond period of illumination at position as and a sec- 0nd period ofdarkness at position 95. It is this double cycle of illumination anddarkness which is carried through the amplifying and decoding systemsand is impressed on a counting system Tl, T2 and T3 to determine theworkability of all the photoelectric cells. Fig. 3 illustrates theentire circuit in block form and shows the two groups of photoelectriccells 32 and 35 connected to the input circuits of six amplifiers aswhich in turn are connected to twelve output circuits 4B. The wiringdetails of amplifiers 45 and 45 are shown in Fig. 6. The output fromamplifiers 46 are applied to a decoding circuit 41 which decodes thePowers code and produces signals for a utilization circuit. One electricpulse is produced for each numeral from zero to nine and for each letterof the alphabet. The output circuits carrying these signals are notshown in Fig. 3 since they do not represent part of this invention. Thedecoding circuit 41 may be a system of relays, a system of neon lamps ora system which uses a number of rectifier components. A decoder usingrectifiers has been described in an article published in the Proceedingsof the Institute of Radio Engineers in June 1949, page 139. The decodingsystem is arranged so that whenever all six of either group ofphotoelectric cells receive full illumination, a pulse will betransmitted over conductor 5!! to a trigger circuit 5! and whenever allthe photo cells are in darkness 9. similar pulse will be transmittedover conductor 52 to a trigger circuit 53.

It has been found necessary to provide an energizing pulse to thedecoder and to the amplifier components is so that the period oftransition from one column position to another will have no effect fromthe output circuit. This energizing circuit is controlled by a slottedWheel 54 (Fig. 3) revolving in synchronism with the sensing drum 23. Asource of light '55 illuminates the slots in wheel '55 and thetransmitted pulses of illumination are applied to a photoelectric cell56. The output from the photoelectric cell 56 is applied to amplifyingsystems 51, 58 which are shown in greater detail in Fig. 5 and oneoutput from this amplifier is applied over conductor 66 to all thetwelve amplifier units 46. Another output from amplifier 5? is appliedto a fast vibrating relay 6! which produces a closed circuit by means ofcontacts 52. These contacts connect a 100-volt supply to the decodingsystem 47 by means of conductor 83.

The slots in wheel 54 are arranged so that light is transmitted to thephotoelectric cell 5S while the card on the sensing drum 23 passes overthe central portion of the sensing position. Wheel 4 containsninety-five slots ninety code positions in the data card plus the fivepositions between cards as illustrated in Fig. 4. Trigger circuits 5|and 53 are commonly called Schmitt triggers and comprise two triodeelectron discharge devices, one of which triodes is always conductingwhile the other triode is non-conducting. By raising the voltage apredetermined amount on the input conductors 50, 52, conductance isshifted from one triode to the other and upon removal of the inputvoltage, conductance immediately shifts back to its normal position.Since trigger stage 53 operates when all photoelectric cells are dark,an indication will be received over conductor 52 each time a blankcolumn is sensed in the card. The transmittal of this informationdesignating a space is necessary during the normal card sensing processand such information is transmitted to the printing or tabulatingcircuit over a conductor 64. During the normal card sensing procedurethese space pulses are not transmitted to the counting circuit asrepresented by triggers Tl, T2 and T3 because a gate circuit $5 isclosed and information from trigger circuit 53 will not be transmittedthrough it.

The counting circuit for determining the workability of photoelectriccells 32, 35 include three trigger circuits 55, 61 and 68. These are theusual double triode type of trigger circuits in which one triode isalways conducting and the other is nonconducting. A transfer ofconductance from one triode to another is accomplished by actuating thecircuit with a short negative pulse. When trigger circuits of this typehave been actuated, the conductance shifts from one triode to anothercorresponding to the and remains in the actuated condition until asecond negative pulse has been received, transferring it back to itsoriginal position. The counting circuit also includes an amplifier stageit which is convenient but not necessary to its operation. The output ofamplifier 70 is connected to a relay coil H and relay contacts 72 arepart of a signal circuit which will either operate a signal I28 or elsedisengage a clutch l2! to stop the machine. Since this counting circuitoperates only between the sensing of two cards, it is held inoperativeduring the card sensing operation and energized into operating conditionby a negative pulse which is transmitted through a commutator segment13. A commutator arm 74 rotates on shaft 15 which may be directlyconnected to shaft 24 operating the sensing drum or to shaft 54A whichturns the slotted wheel 54. The voltage pulse sent through segment 73 istransmitted through a neon lamp it and through a blocking condenser 77to trigger stage 68 to actuate it and at the same time open gate stage65 by increasing the voltage on conductor I I5, placing the countingcircuit in the operative condition. The details of the counting circuitoperations will be described hereinafter.

The circuit shown in Fig. 5 includes the photoelectric cell 56 and theamplifiers 5'! and 58 shown in block form in Fig. 3. The amplifiercircuit includes a pentode tube 89, a Schmitt trigger t2 and anunbalanced trigger circuit 85, sometimes called a flip-flop, and twooutput amplifier stages st and 85. Amplifier 84 is connected to a relaywinding El and makes and breaks contacts E2 when the tube circuit isactuated. Output amplifier 86 is a cathode-follower stage and transmitspulses over conductor 68 to the gasfilled amplifier stages shown indetail in Fig. 6. The photoelectric cell 56 receives flashes of lightthrough rotating slotted disc 54. These periods of illumination areconverted into voltage pulses which are amplified by the pentode 80 andtransmitted by conductor 8| to Schmitt trigger 82 which is normallyconducting on the right side. When the photoelectric cell isilluminated, the passage of current through the tube causes the controlgrid of tube 86 to be increased in potential, thereby increasing theflow of current through the tube and lowering the potential of theanode. This causes the control electrode of the right triode in tube 82to receive a negative pulse and conductance is transferred to the leftside. This transfer raises the potential of the right anode and apositive pulse is applied to both control electrodes in amplifier stage84, thereby drawing current through the tube through winding 5! andmaking contacts 62. When these contacts are made, a potential increaseof 109 volts is applied to conductor 63 which goes to the decodercircuit M.

The decrease of potential on the left anode in tube 82 is alsocommunicated over conductor 81 to the unbalanced trigger circuit 35. Theconductance in this tube is transferred for a short interval of time tothe left triode and then the conductance is transferred back again dueto the operation of the circuit components. This fluctuation produces asquare top voltage wave which is applied over conductor 88 throughcathodefollower amplifier 86 and results in a square top wave beingapplied to all the amplifier stages 46 by way of conductor 66. Theseries of light and dark fiashes which are applied to the photoelectriccell 56 are synchronized with the column positions of the data cards asthey are sensed by the sensing drum. The circuit shown in Fig. 6 is theamplifier which receives electric impulses from the two groups 32, 35 ofsix photoelectric cells as indicated in Fig. 3 and also in Fig. 6.Corresponding photo cells from each group are connected in parallel witheach other.

The amplifier which receives the electric output from the photo cellscomprises a first pentode tube amplifier I00, a double triode amplifierstage fill, and two gas-filled discharge devices Hi4 and H15. When lightfrom a data hole is impressed on one of the tubes 32 or 35, the currentthrough its electrodes is increased and the control electrode ofamplifier tube Hill is increased in value, thereby sending a relativelylarge current through the tube and reducing the potential of the anode.This action is communicated to the left control electrode of the Schmitttrigger stage Hit and conductance is thereby shifted from the left tothe right side. This action increases the potential on conductor m3 andplaces the tube 564 in a firing condition. Then when the controlpotential is applied over conductor 60, the tube is fired and a negativepotential is sent over conductor we to the decoding matrix. When thereis no hole in the data card and photoelectric cells 32 and 35 are indarkness, the anode of stage ill!) will be at its most positive valueand Schmitt trigger stage Hll Will retain its conductance on the leftside. This puts a negative potential on the screen grid of tube I04 butputs a positive potential on the screen grid of tube [05. In thiscondition when the voltage pulse is applied over conductor 60, tube Hwill be fired and a large negative pulse will be sent out over conductorID? to the decoding matrix, thereby indicating that no hole is presentin the card in this position.

The circuit shown in Fig. '7 represents the details of the stagesconnected to the output of the decoder matrix i! and were shown in blockform in Fig. 3. The circuit contains two Schmitt triggers 5i and 53', agate stage 65, three trigger stages til, 6?, and B8 and an amplifierstage Iii. The Schrnitt trigger 53 is actuated only when all six photoelectric cells are in darkness, thereby indicating a space. Theactuation of this stage sends a positive potential over conductor IE8 toa voltage divider connected to the control electrode of gate stage 65.If the gate stage is open, a pulse is transmitted through ductor ills toactuate the first trigger stage 6%. If the gate stage is closed, nothinghappens. When all six photoelectric tubes are illuminated, an increasein potential is sent over conductor 58 to Schmitt trigger stage 5!,ferring its conductance to the right side and sending a negative voltagepulse over conductor H I to the right-hand control electrode of thefirst trigger stage 66. If such a pulse is received by the trigger stagewhen in its normal condition, nothing happens since the pulse simplymakes a negative electrode more negative. On the other hand, if triggerstage as had first been actuated by a pulse through stages 53 and E55,then the actuation of stage 5| Will transfer the conductance back tonormal.

The first trigger stage 66 has the usual coupling conductor H2 so thatwhen its conductance is normalized, a negative pulse is sent over thisconnection to both control electrodes of the second trigger stage 61,actuating this stage and transferring its conductance from one side tothe other regardless of the previous conductive position. The secondtrigger stage 61 contains a similar coupling conductor l l3 which isconnected the gate by Way of con-- thereby transa conductor 52 totrigger stage 53,

to the right-hand control electrode of the third trigger stage 6'3 andwhenever the conductance of stage 61 is transferred from right to left,a negative voltage is sent over conductor H3 to actuate trigger stage 68if the conductance had been previously transferred to the right side.

When the counting circuit as shown in Fig. 7 is in its normal orzeroized condition, the gate stage is closed and the five trigger stagesare all conducting on the left side, the amplifier stage it isconducting and contacts 12 are held open. This zero or normalizedcondition is maintained throughout the sensing of the data card exceptfor the sensing of a space and the actuation of stage 53. The actuationof this stage during the normal sensing operation causes a positivepulse to be sent over conductor 64 to other parts of the circuit butsince the gate stage is closed, the counting circuit is not affected.When the ninety-first column on the sensing drum is reached, acommutator arm 14 makes contact with a segment 13 and a negativepotential of '75 volts is transmitted over conductor H4 through a neonlamp l6, lighting the lamp and impressing a negative potential on theleft control electrode of the third trigger stage 58 through blockingcapacitor 11. This voltage pulse causes the actuation of stage 68,transferring the conductance to the right side and by so doing, raisingthe potential of conductor H5 and impressing a positive potential on thecon trol electrode of gate stage 65 and increasing the potential of thecontrol electrode to a value which is one or two volts below the cut-offpotential. In this condition the gate is said to be open because apositive potential applied over conductor H36 will increase thepotential of the control electrode to a value which permits current toflow from the anode to the cathode in stage 55 and a negative pulse willbe sent out over conductor 19.

During the time the ninety-first column is in the sensing position, alltwelve photoelectric cells are dark and a positive pulse is transmittedover transferring its conductance to the right side. This sends apositive pulse over conductor I08 to gate stage 65 which is now open anda negative pulse is sent over conductor we to the left control electrodeof stage 56, transferring its conductance to the right side. Just beforethe ninety-first column passes out of the sensing position the voltageon conductor 53 is reduced to zero and the decoding matrix isole-energized, thereby eliminating the voltage on conductor 52. Thiscauses trigger stage 53 to be returned to its normal condition.

When the ninety-second column appears in the sensing position, slot M(Fig. l) illuminates all sin of the photo cells in group 32 and apositive pulse is sent over conductor 50 to trigger stage 5i,transferring its conductance to the right side and sending a negativepulse over conductor Hi to trigger stage 66. Conductance of stage it istransferred from the right to the left side and at the same time a carrypulse is sent over conductor H2 to actuate trigger stage 67 and causeits conductance to be transferred to the right side. Near the end ofthis time interval, stage 5i is normalized.

When the ninety-third column is moved into the sensing position, all thephotoelectric cells are in darkness and a positive pulse is again sentover conductor 52 to actuate stage 53 to change its conductance to theright side. As before, a positive pulse is sent over conductor I08through gate stage 65 and appears as a negative pulse on conductor I99and. actuates trigger stage 66, causing its conductance to be againshifted from left to the right. During this time interval, neitherstages 61 or 68 are actuated. As the column position 93 moves away fromthe sensing posi-- tion, stage 53 is normalized.

When the ninety-fourth column is moved to the sensing position, the sixphotoelectric cells in group 35 all receive illumination and a posi tivepulse is transferred over conductor 50 to stage thereby sending anegative pulse again over conductor II I to stage 66, transferring itsconductance back to normal and sending a carry pulse over conductor IE2to trigger stage 67, transferring its conductance back to the normal orleft side. This in turn sends a negative pulse over conductor H3 to thethird trigger stage 68 which has been conducting on the right side sinceits first actuation by the negative voltage on segment 13. Stage 68 isactuated and returned to the left or normal condition, thereby applyinga negative voltage on conductor H5 which will lower the potential on thecontrol electrode of gate stage 65 sufficiently to close the gate andnot permit subsequent conduction.

When the ninety-fith column is moved to the sensing position, all twelvephotoelectric cells are in darkness and a positive pulse is again sentover conductor 52 to actuate stage 53 and change its conductance to theright. At this time, gate stage 55 is closed and nothing furtherhappens.

During the normal sensing of the data card, amplifier stage It isconducting current between the anode and cathode. This conduction is dueto the fact that the control electrode of stage in is above the cut-offvoltage since conductor I22 receives a positive potential from the thirdtrigger stage 68. Because of the conduction in stage iii, relay winding1| carries current and contacts is are held open. When trigger stage 538is actuated and its conductance is transferred to the right, a loweredpotential appears on conductor i222 and amplifier stage H! is renderednon-conducting and the current in coil H is reduced to zero. Theactuation of trigger stage 58 occurs during the sensing of column SI andthis condition prevails until column 94 when a full count of fourperiods transfers conductance I in stage 68 back to normal andconduction through stage lib is resumed. If relay H, 12 were a fastacting relay, contact l2 would be broken and the signal |2fi would beenergized or clutch 52! would be disconnected. However, i

a delayed. action is built into the relay and contact It: will not openfor the short period of time which consumed in sensing columns cl, 522,and 93. This delayed action is necessary to keep the machine running andto show no signal which would otherwise designate an error in thesensing circuit. In case one of the photoelectric cells does not producecurrent when it is illuminated or produces a current when it has noilluinination, then a full count of four will not be received by thethree trigger circuits 66, ii], and and the last trigger circuit 58 willnot be normalized to conduct on the left side. This condition retainsstage it! in its non-conducting condition and contacts 22 will be made ashort time after the next card has started through the first sensingposition. Then the signal circuit 128 will be energized and the clutchIZI will be disengaged.

Fig. 8 is a chart showing the position of corn ductivity in the fivetrigger stages and also designating the condition of gate stage andamplifier stage id.

Fig. 9 further illustrates the operation and the condition of thetrigger stages by showing the pulses received by the stages in order tooperate them. The pulses received by Schmitt trigger stages SI and S2are positive pulses. All the other operating pulses are negative. In theabove description pulse counting was done by trigger circuits because oftheir speed of operation and because of their reliability. However. itwill be obvious that a similar counting arrangement could have beeenperformed by relay circuits, such counting circuits being old in theart. The gate stage 65 could also be replaced by a relay circuit.

While there have been described and illustrated, specific embodiments ofthe invention, it will be obvious that various changes and modificationsmay be made therein without departing from the field of the inventionwhich should be limited only by the scope of the appended claims.

What is claimed is:

1. A photoelectric checking system for determining the workability of aseries of photoelectric cells comprising; means for applying one or morecycles of luminous energy to said cells, each cycle including a periodof light and a period of darkness; an amplifying and decoding circuitconnected to said series of cells for producing a first electric pulsewhen all of said cells are conducting, and for producing a secondelectric pulse when all of said cells are non-conducting; a pulseresponsive circuit connected to said decoding circuit for receiving saidfirst and second electric pulses; and a signal circuit connected to thepulse responsive circuit for producing a signal when ever the pulseresponsive circuit does not receive all of said pulses.

2. A photoelectric checking system for determining the workability of aseries of photoelectric cells comprising; means for applying one or morecycles of luminous energy to said cells, each cycle including a periodof light and a period of darkness; an amplifying and decoding circuitcon nected to said series of cells for producing a first electric pulsewhen all of said cells are conducting, and for producing a secondelectric pulse when all of said cells are non-conducting; a pulseresponsive circuit connected to said decoding circuit for receiving saidfirst and second electric pulses; and a signal circuit connected to thepulse responsive circuit for producing a signal whenever the pulseresponsive circuit fails to transmit all of the pulses corresponding tothe cycles of luminous energy.

3. A photoelectric checking system for determining the workability of aseries of photoelectric cells comprising; means for applying one or morecycles of luminous energy to said cells, each cycle including a periodof light and a period of darkness; an amplifying and decoding circuitconnected to said series of cells for producing a first electric pulsewhen all of said cells are conducting, and for producing a secondelectric pulse when all of said cells are non-conducting; a countingcircuit connected to the decoding circuit for counting said first andsecond electric pulses; and a signal circuit connected to the countingcircuit for producing a signal whenever the counting circuit does notcount all of said periods.

4. A photoelectric checking system for determining the workability of aseries of photoelectric cells comprising; means for applying one or morecycles of luminous energy to said cells, each cycle including a periodor light and a period of dark ness; an amplifying and decoding circuitconnected to said series of cells for producing a first electric pulsewhen all of said cells are conducting, and for producing a secondelectric pulse when all of said cells are non-conducting; a countingcircuit connected to the decoding circuit and including a series ofelectronic trigger stages for counting said first and second electricpulses; and a signal circuit connected to the counting circuit forproducing a signal whenever the counting circuit does not count all orsaid periods.

5. A photoelectric checking system for deter mining the workability of aseries of photoelectric cells comprising; means for applying one or morecycles of luminous energy to said cells, each cycle including a periodof light and a period of darkness; an amplifying and decoding circuitconnected to said series of cells for producing a first electric pulsewhen all of said cells are con ducting, and for producing a secondelectric pulse when all of said cells are non-conducting; a countingcircuit for counting said first and second electric pulses; saidcounting circuit comprising, a gate stage which transmits countingpulses only when open, a series of trigger stages connected to the gatestage, and means for opening the gate stage at the start of said cyclesof luminous energy; and a signal circuit connected to the countingcircuit for producing a signal whenever the counting circuit does notcount all of said periods.

6. A photoelectric checking system for determining the workability of aseries of photoelectric cells comprising; means for applying one or morecycles of luminous energy to said cells, each cycle including a periodof light and a period of darkness; an amplifying and decoding circuitconnected to said series of cells for producing a first electric pulsewhen all of said cells are conducting, and for producing a secondelectric pulse when. all or said cells are non-conducting; a countingcircuit for counting said first and second electric pulses; saidcounting circuit comprising, a gate stage which transmits countingpulses only when open, a series of trigger stages connected to the gatestage, and a commutator connected between the gate stage and a source ofpotential for opening the gate stage at the start of said cycles ofluminous energy; and a signal circuit connected to the counting circuitfor producing a signal whenever the counting circuits does not count allof said periods.

'7. A photoelectric checking system for determining the workability of aseries of photoelectric cells comprising; means for applying one or morecycles of luminous energy to said cells, each cycle including a periodof light and a period of darkness; an amplifying and decoding circuitconnected to said series of cells for producing a first electric pulsewhen all of said cells are conducting, and for producing a secondelectric pulse when all of said cells are non-conductingg a countingcircuit for counting said first and second electric pulses; saidcounting circuit comprising, a gate stage which transmits countingpulses only when open, a series of trigger stages connected to the gatestage, and a commutator connected between the gate stage and a source ofpotential for opening the gate stage at the start of said cycles ofluminous energy; a signal circuit connected to the counting circuit forproducing a signal whenever the counting circuit does not count all orsaid periods; and means for closing the gate stage when all of saidperiods have been counted.

8. A photoelectric checking system for determining the workability of aseries of photoelectric cells comprising; means for applying one or morecycles of luminous energy to said cells, each cycle including a periodof light and a period or darkness; an amplifying and decoding circuitconnected to said series of cells for producing a first electric pulsewhen all of said cells are conduct ing, and for producing a secondelectric pulse when all of said cells are non-conducting; a countingcircuit for countin said first and second electric pulses; said countingcircuit comprising, a series of trigger stages connected in a countingarrangement and receiving input pulses through a gate stage, aconnection between one of the trigger stages and the gate stage wherebythe gate stage is opened when said trigger stage is actuated and thegate sta e is closed when the trigger stage is normalized; a commutatorconnected between said trigger stage and a source of potential foractuating the trigger stage at the start or said cycles of luminousenergy; a signal circuit connected to the counting circuit for produringa signal whenever the counting circuit does not count all of saidperiods; and counting circuit means for normalizing said trigger stageand closin the gate stage when all of said periods have been counted.

9. A photoelectric checking system for determining the workability of aseries of photoelectric cells comprising; means for applying one or morecycles or luminous energy to said cells, each cycle including a periodof light and a period of darkness; an amplifying and decoding circuitconnected to said series of cells for producing a first electric pulsewhen all of said cells ar conducting, and for producing a secondelectric pulse when all of said cells are non-conducting; a countingcircuit for counting said first and sec- 0nd electric pulses; saidcounting circuit comprising, an input circuit connected through a gatestage, a series of trigger stages connected to the input circuit andincluding an output trigger stag connected to a signal circuit, aconnection between the output trigger stage and the gate stage to openthe gate stage whenever the output stage is actuated. and to close thegate stage when the output stage is normalized; means for actuating theoutput trigger stage at the start of said cycles of luminous energy; asignal circuit connected to the counting circuit for producing a signalwhenever the counting circuit does not count all of said periods; and acounting circuit connection for sending an electrical pulse to theoutput trigger sta e to normalize it when all. of said periods have beencounted.

10. A photoelectric checking system for determining the workability of aseries of photoelectric cells arranged in two sensing groups comprising;means for sequentially applying a cycle of luminous energy to each groupof cells, each cycle including a period of light and a period ofdarkness; an amplifying and translating circuit con nected to saidgroups of photoelectric cells for producing a first electric pulse whenall the cells in either group are conducting, and for producing a secondelectric pulse when all cells in both groups are non-conducting; a pulseresponsive circuit connected to said translating circuit for receivingsaid first and second electric pulses; and a signal circuit connected tothe pulse responsive circuit for producing a signal whenever the pulseresponsive circuit does not receive all of said pulses.

11. A photoelectric checking system for determining the workability of aseries of photoelectric cells arranged in two sensing groups comprising;means for sequentially applying a cycle of luminous energy to each groupof cells, each cycle including a period of light and a period ofdarkness; an amplifyin and translating circuit connected to said groupsof photoelectric cells for producing a first electric pulse When all thecells in either group are conductin and for producing a second electricpulse when all cells in both groups are non-conducting; a pulseresponsive circuit connected to said translating circuit for receivingsaid first and second electric pulses; and a signal circuit connected tothe pulse responsive circuit for producing a signal whenever the pulseresponsive circuit fails to transmit all of the pulses corresponding tothe cycles of luminous energy applied to both groups of photoelectriccells.

12. A photoelectric checking system for determinin the workability of aseries of photoelectric cells arranged in two sensing groups comprising;means for sequentially applying a cycle of luminous energy to each groupof cells, each cycle including a period of light and a period ofdarkness; an amplifying and translating circuit connected to said groupsof photoelectric cells for producing a first electric pulse when all thecells in either group are conducting, and for producing a secondelectric pulse when all cells in both groups are non-conducting; acountin circuit connected to the translating circuit for counting thefirst and second electric pulses from each group; and a signal circuitconnected to the counting circuit for producing a signal whenever thecounting circuit fails to count all the periods from both groups ofcells.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,231,186 Gould Feb. 11, 1941 2,473,314 Toulon June 14, 19492,563,274 Rendel Aug. 7, 1951

